1. Field of the Invention
The present invention relates to an apparatus and method for manufacturing a spiral duct, and more particularly, to an apparatus and method for manufacturing a spiral duct capable of readily manufacturing a spiral duct in which straight connection parts are integrally formed with both ends of a curved duct, and securely coupling a bent part formed at a straight edge with a bent part formed at a waved part to prevent generation of inferior products by smoothly cutting a metal band along a waved line in its longitudinal direction.
2. Description of the Prior Art
A curved duct in which a band-shaped metal plate is wound in a spiral shape, and side edges of the metal plate are hooked and coupled to each other is disclosed in several prior arts.
However, in the prior arts, since the metal band is continuously cut to form large width parts and small width parts and then residual parts are discarded, the metal band is wasted.
In order to prevent waste of the material, Korean Patent Laid-open Publication No. 1990-17678 discloses “METAL BAND FOR MANUFACTURING SPIRAL DUCT”, as shown in FIG. 1.
Specifically, a single sheet of metal band is cut into two metal bands, each of which has large width parts and small width parts, which are alternately formed in its longitudinal direction. That is, each of the metal bands has one straight side edge and the other waved side edge, thereby minimizing waste of the metal band.
Using one of the two metal bands, a dual bent part is formed at the straight side edge and a single bent part is formed at the waved side edge along the entire length in an upright posture. The metal band is wound in a spiral manner, and simultaneously, the large width part is positioned at an outer curved part and the small width part is positioned at an inner curved part. Next the single bent part and the dual bent part, which are adjacent to each other, are sequentially inserted and then pressed to complete the curved duct.
FIG. 2 shows a conventional apparatus for manufacturing a curved duct.
As shown, a metal band 3 is extracted between first forming rollers 11 of the apparatus for manufacturing a curved duct to form two L-shaped bent parts 4 at both side edges of the metal band 3.
Next, the L-shaped bent parts 4 are bent again by a pair of upper and lower forming rollers 14 disposed in front of the first rollers 11 to form approximately C-shaped dual bent parts 5.
Then, as shown in FIG. 3, the metal band 3 having the dual bent parts 5 is cut and divided by a female roller 18 having a waved groove 17 formed at its outer periphery and the same diameter as the curved duct, and a male roller 20 having a waved blade 19 corresponding to the waved groove 17.
In addition, at the same time the metal band 3 is cut, both cut edges are pushed into the groove 17 by the blade 19 to form L-shapes, thereby forming a pair of single bent part 6.
Further, as shown in FIG. 4, the single bent parts 6 of the two metal bands 2 are bent toward the dual bent parts 5 by an upper support roller 21 disposed in the front, and a third lower forming roller 25 having an approximately diamond shape and axially supported by a bearing 24 of a slider 23 slidably inserted into a horizontal guide shaft 22.
As described above, the conventional apparatus for manufacturing a curved duct includes the male roller 20 having the waved blade 19 formed at its outer periphery, and the female roller 18 having the waved groove 17 corresponding to the waved blade 19, to thereby cut a metal band between the waved blade 19 and the waved groove 17.
In addition, as shown in FIG. 5, the spirally wound metal band is manufactured by contacting the waved edge with the straight edge, and pressing forward by a reciprocating roller 36 such that the reciprocating roller 36 moves backward at a convex part of the waved edge and moves forward at a concave part of the waved edge, thereby automatically coupling the dual bent part 5 with the single bent part 6.
However, when the metal band is cut by the roller having the blade or the groove formed at its outer surface, it is not possible to cut a metal band having a predetermined length of straight part. As a result, it is difficult to manufacture a duct in which straight connection ducts are integrally formed with both ends of a curved duct.
In addition, when the metal band is cut by the roller having the blade or the groove formed at its outer surface, the cut part may be readily rough, and thus, it is difficult to precisely form the single bent part and securely couple the single bent part with the dual bent part.